Mechanisms for radical reactions initiating from N-hydroxyphthalimide esters

• Carlos R. Azpilcueta-Nicolas and
• Jean-Philip Lumb

Beilstein J. Org. Chem. 2024, 20, 346–378, doi:10.3762/bjoc.20.35

• photocatalytic radical-mediated dearomatization, with H2O serving as the nucleophile [54] (Scheme 9A). Despite the presence of H2O in the reaction, the reduction of 38 to its corresponding radical anion 39 could occur without the need for hydrogen-bonding (Scheme 9B). Cyclic voltammetry measurements of NHPI

• photoquenching experiments confirmed that 38 effectively quenched *Ir(ppy)3 under anhydrous conditions. Consequently, the SET reduction of 38, followed by fragmentation of 39 yielded α-oxy radical intermediate 40. Subsequently, the spirocyclization of 40 induced the dearomatization of the methoxy-substituted

Photoredox catalysis harvesting multiple photon or electrochemical energies

• Mattia Lepori,
• Simon Schmid and
• Joshua P. Barham

Beilstein J. Org. Chem. 2023, 19, 1055–1145, doi:10.3762/bjoc.19.81

• indoline scaffolds (22a,b) via a radical-polar crossover mechanism (Figure 12C) [65], showcasing the power of conPET in dearomatization reactions. Finally, the synthesis of tetraphenylphosphonium chloride (20a) could be scaled up efficiently in an operationally very simple continuous-flow setup with only

Synthesis of tetrahydrofuro[3,2-c]pyridines via Pictet–Spengler reaction

• Elena Y. Mendogralo and
• Maxim G. Uchuskin

Beilstein J. Org. Chem. 2023, 19, 991–997, doi:10.3762/bjoc.19.74

• the use of 3-substituted furans. For example, the intramolecular Friedel–Crafts alkylation reaction (Scheme 1a) of alcohols [9][10][11], alkenes [12] or acetylenes [13] affords the desired tetrahydrofuro[3,2-c]pyridines. A related method is based on a Au(I)-catalyzed domino sequence dearomatization

Combining the best of both worlds: radical-based divergent total synthesis

• Kyriaki Gennaiou,
• Antonios Kelesidis,
• Maria Kourgiantaki and
• Alexandros L. Zografos

Beilstein J. Org. Chem. 2023, 19, 1–26, doi:10.3762/bjoc.19.1

• commenced with the generation of 107 from cyclopentenone 105 and aryl aldehyde 106 in a three-step sequence. An oxidative dearomatization induced a [5 + 2] cycloaddition–pinacol rearrangement of 107 to 109, according to previous studies of the same group (Scheme 9) [59][60][61]. The key HAT-mediated

Total synthesis of grayanane natural products

• Nicolas Fay,
• Rémi Blieck,
• Cyrille Kouklovsky and
• Aurélien de la Torre

Beilstein J. Org. Chem. 2022, 18, 1707–1719, doi:10.3762/bjoc.18.181

• group on C6 was introduced after cyclopropane ring-opening, ketone protection, epoxidation and reductive ring-opening of the resulting epoxide. A one-pot β-keto phosphonate formation/Horner–Wadsworth–Emmons reaction with formaldehyde afforded 38, a precursor for the key oxidative dearomatization-induced

• have a bicyclo[2.2.2]octane precursor, which can be obtained by a dearomatization/Diels–Alder cascade. For Luo, the 1,2-shift forms bond C12–C13 through a cationic Wagner–Meerwein-type rearrangement. The B ring is obtained by a key bridgehead carbocation trapping, while the skeleton arises from an A

Synthetic strategies for the preparation of γ-phostams: 1,2-azaphospholidine 2-oxides and 1,2-azaphospholine 2-oxides

• Jiaxi Xu

Beilstein J. Org. Chem. 2022, 18, 889–915, doi:10.3762/bjoc.18.90

• - and stereoselectivities in the tandem intramolecular nucleophilic dearomatization of diphenyl-N-alkyl-N-benzylphosphinamides and reactions with different electrophiles under various reaction conditions [47]. They used both racemic and enantiopure diphenyl-N-methyl-N-(1-phenylethyl)phosphinamides 124

• intramolecular nucleophilic dearomatization and protonation or electrophilic alkylation reactions, affording the corresponding dihydronaphthylene-fused γ-phosphinolactams 135–142. Methanol was used as the electrophile for protonation, while methyl iodide and allyl bromide were used as electrophiles for

Regioselectivity of the S_EAr-based cyclizations and S_EAr-terminated annulations of 3,5-unsubstituted, 4-substituted indoles

• Jonali Das and
• Sajal Kumar Das

Beilstein J. Org. Chem. 2022, 18, 293–302, doi:10.3762/bjoc.18.33

• -cd]indoles 21 from the intramolecular cyclization of Ugi adducts 20 in moderate to good yields and excellent chemo-, regio-, and diastereoselectivity (Scheme 7) [17]. Mechanistically, the reaction involves a tandem gold(I)-catalyzed dearomatization/ipso-cyclization/Michael addition sequence to

Iron-catalyzed domino coupling reactions of π-systems

• Austin Pounder and
• William Tam

Beilstein J. Org. Chem. 2021, 17, 2848–2893, doi:10.3762/bjoc.17.196

• 74. Hydrolysis of the imine affords the final product 69. In 2020, Sun and Liu reported the iminyl cyclization could also be achieved with DMSO as a methyl-radical precursor [88]. In 2017, the Zhu group developed an Fe(acac)3-catalyzed cyanoalkylative dearomatization of N-phenylcinnamamides 75 for

• of the aryl ring, a spirocyclic product 145 was formed via a radical cyclization/dearomatization process. Mechanistic investigations revealed the reaction operates through a radical pathway. In 2017, the Li group described a Ag-mediated, Fe-catalyzed alkylarylation of styrene derivatives 115 with α

Recent advances in the asymmetric phosphoric acid-catalyzed synthesis of axially chiral compounds

• Alemayehu Gashaw Woldegiorgis and
• Xufeng Lin

Beilstein J. Org. Chem. 2021, 17, 2729–2764, doi:10.3762/bjoc.17.185

• phosphoric acid catalysis, we developed a highly regio-, diastereo-, and enantioselective dearomatization reaction of 1-substituted 2-naphthols 115 and β,γ-alkynyl-α-imino esters 100. The highly functionalized naphthalenone derivatives 116 with an allene moiety, exhibiting both a quaternary stereocenter and

Halides as versatile anions in asymmetric anion-binding organocatalysis

• Lukas Schifferer,
• Martin Stinglhamer,
• Kirandeep Kaur and
• Olga García Macheño

Beilstein J. Org. Chem. 2021, 17, 2270–2286, doi:10.3762/bjoc.17.145

• ) [35]. During this early period, the group of Jacobsen also reported an asymmetric thiourea-catalyzed Reissert reaction of isoquinolines 21 (Scheme 5a) [36]. The mechanism proceeds by initial activation of the isoquinoline via N-acylation and subsequent dearomatization by a nucleophilic attack in the

Synthetic accesses to biguanide compounds

• Oleksandr Grytsai,
• Cyril Ronco and
• Rachid Benhida

Beilstein J. Org. Chem. 2021, 17, 1001–1040, doi:10.3762/bjoc.17.82

• benzothiazole and benzimidazole-based sulfonylguanidine compounds were derived by the sulfonylation of the corresponding 2-guanidinobenzazoles and assayed as potential antimelanoma agents (Scheme 11C) [33]. Of note, a dearomatization of the benzothiazole ring was observed while grafting a sulfoguanidinyl group

Synthetic reactions driven by electron-donor–acceptor (EDA) complexes

• Zhonglie Yang,
• Yutong Liu,
• Kun Cao,
• Xiaobin Zhang,
• Hezhong Jiang and
• Jiahong Li

Beilstein J. Org. Chem. 2021, 17, 771–799, doi:10.3762/bjoc.17.67

• the dearomatization of β-naphthol promoted by visible light via intermolecular charge transfer (Scheme 29). In this method, β-naphthol anion 87 (β-naphthol 85 formed in the presence of base) is employed as electron donor to form EDA complex with electron acceptor perfluoroalkyl iodide 28. Single

Copper catalysis with redox-active ligands

• Agnideep Das,
• Yufeng Ren,
• Cheriehan Hessin and
• Marine Desage-El Murr

Beilstein J. Org. Chem. 2020, 16, 858–870, doi:10.3762/bjoc.16.77

• ], and perform C–H functionalization through aerobic dearomatization of phenols [35]. These broad synthetic outcomes further led to a unified approach for the preparation of 1,2-oxy-aminoarenes by phenol–amine couplings (Scheme 10) [36]. We reported the formation of a C–N bond through copper-catalyzed

Preparation and X-ray structure of 2-iodoxybenzenesulfonic acid (IBS) – a powerful hypervalent iodine(V) oxidant

• Irina A. Mironova,
• Pavel S. Postnikov,
• Rosa Y. Yusubova,
• Akira Yoshimura,
• Thomas Wirth,
• Viktor V. Zhdankin,
• Victor N. Nemykin and
• Mekhman S. Yusubov

Beilstein J. Org. Chem. 2018, 14, 1854–1858, doi:10.3762/bjoc.14.159

• of phenols to 1,2-quinones [15], the cyclization and cross-coupling reactions [16], and the site-selective hydroxylative dearomatization of 2-substituted phenols to either 1,2-benzoquinols or their cyclodimers [17]. The first preparation and isolation of IBS (1) was attempted in 2006 using two

Synthesis of spirocyclic scaffolds using hypervalent iodine reagents

• Fateh V. Singh,
• Priyanka B. Kole,
• Saeesh R. Mangaonkar and
• Samata E. Shetgaonkar

Beilstein J. Org. Chem. 2018, 14, 1778–1805, doi:10.3762/bjoc.14.152

• stoichiometric or catalytic amounts. In addition, hypervalent iodine reagents have been employed for the synthesis of spirocyclic scaffolds via dearomatization processes. In this review, various approaches for the synthesis of spirocyclic scaffolds using hypervalent iodine reagents are covered including their

• who want to know the chemistry involved during the dearomatization of phenols and to find the relevant literature available until 2008. In this review article, various approaches for the synthesis of spirocyclic scaffolds using hypervalent iodine reagents are covered including stereoselective

• I (30) to its spirocyclic analogue arnottin II (32) by reaction with LiOH followed by PIFA (31). The spirocyclic product arnottin II (32) was isolated in 56% yield (Scheme 7). This approach is based on a tandem oxidative dearomatization process and will be quite useful for the conversion of

Cobalt-catalyzed C–H cyanations: Insights into the reaction mechanism and the role of London dispersion

• Eric Detmar,
• Valentin Müller,
• Daniel Zell,
• Lutz Ackermann and
• Martin Breugst

Beilstein J. Org. Chem. 2018, 14, 1537–1545, doi:10.3762/bjoc.14.130

• comparison with previous computational investigations on copper-catalyzed ortho C–H cyanations of vinylarenes revealed that those reactions take place via a completely different mechanism involving two distinct catalytic cycles (copper-catalyzed electrophilic cyanative dearomatization and base-catalyzed

Hypervalent organoiodine compounds: from reagents to valuable building blocks in synthesis

• Gwendal Grelier,
• Benjamin Darses and
• Philippe Dauban

Beilstein J. Org. Chem. 2018, 14, 1508–1528, doi:10.3762/bjoc.14.128

• , C–C, C–O, or C–N couplings, dearomatization of phenols, rearrangements, to name but a few, have been reported using these compounds thereby reflecting their versatility. A survey of the general structure of polyvalent organoiodine compounds reveals that they are prepared mostly from iodoarene

A survey of chiral hypervalent iodine reagents in asymmetric synthesis

• Soumen Ghosh,
• Suman Pradhan and
• Indranil Chatterjee

Beilstein J. Org. Chem. 2018, 14, 1244–1262, doi:10.3762/bjoc.14.107

• electrophilicity and appreciable oxidizing properties. The transformations associated with asymmetric induction mainly focused on the asymmetric oxidation and oxidative dearomatization chemistry. Asymmetric difunctionalization of alkenes, α-functionalization of carbonyls and also some typical 1,2-aryl

• ) [31]. A summary of chiral hypervalent iodine reagents used in the asymmetric oxidation of sulfides is sketched below (Scheme 2). Asymmetric oxidative dearomatization, alkene functionalization and rearrangement strategy Oxidative dearomatization Asymmetric oxidative dearomatizations and the use of

• enantioselective oxidative dearomatization of phenolic derivatives 25 (spirolactonization) which is known as Kita oxidation to yield spirocyclic compounds 26 with good enantioselectivity [32]. The indication of an associative mechanism was also confirmed due to an increased enantioselectivity observed in polar

Enantioselective dioxytosylation of styrenes using lactate-based chiral hypervalent iodine(III)

• Morifumi Fujita,
• Koki Miura and
• Takashi Sugimura

Beilstein J. Org. Chem. 2018, 14, 659–663, doi:10.3762/bjoc.14.53

• iodine reagents using a lactate motif has been employed for several types of oxidation reaction since we first reported this procedure [18]. Enantioselective oxidative transformations include the dearomatization of phenols [19][20][21][22][23][24], α-functionalization of carbonyl compounds [25][26][27

Oxidative cycloaddition of hydroxamic acids with dienes or guaiacols mediated by iodine(III) reagents

• Hisato Shimizu,
• Akira Yoshimura,
• Keiichi Noguchi,
• Victor N. Nemykin,
• Viktor V. Zhdankin and
• Akio Saito

Beilstein J. Org. Chem. 2018, 14, 531–536, doi:10.3762/bjoc.14.39

• moderate to high yields. The present method could be applied to the HDA reactions of acylnitroso species with o-benzoquinones generated by the oxidative dearomatization of guaiacols. Keywords: acylnitroso; benzoquinone; cycloaddition; dearomatization; iodine(III); Introduction The hetero-Diels–Alder (HDA

• , we report the HDA reaction of acylnitroso species generated from hydroxamic acids by [bis(trifluoroacetoxy)iodo]benzene (BTI) or DIB. The present method could be applied to HDA reactions with not only simple dienes but also with masked o-benzoquinones (MOBs) generated by the oxidative dearomatization

• NMR analysis). As a further application of the iodine(III)-mediated oxidative cycloaddition reactions, the present method was extended to HDA reactions with masked o-benzoquinones (MOBs) generated by the oxidative dearomatization [26][27][28][29] of guaiacols with methanol (Scheme 2). Liao’s and other

Nucleophilic dearomatization of 4-aza-6-nitrobenzofuroxan by CH acids in the synthesis of pharmacology-oriented compounds

• Alexey M. Starosotnikov,
• Dmitry V. Shkaev,
• Maxim A. Bastrakov,
• Ivan V. Fedyanin,
• Svyatoslav A. Shevelev and
• Igor L. Dalinger

Beilstein J. Org. Chem. 2017, 13, 2854–2861, doi:10.3762/bjoc.13.277

• the design of pharmacology-oriented heterocyclic systems. Keywords: CH acids; dearomatization; 1,4-dihydropyridines; furoxans; nitropyridines; Introduction The reactions of condensed furoxans with CH acidic compounds have been extensively studied. There are two main possibilities for these reactions

Chiral phase-transfer catalysis in the asymmetric α-heterofunctionalization of prochiral nucleophiles

• Johannes Schörgenhumer,
• Maximilian Tiffner and
• Mario Waser

Beilstein J. Org. Chem. 2017, 13, 1753–1769, doi:10.3762/bjoc.13.170

• -worker reported the use of phase-transfer catalysts to carry out the dearomatization of phenol and naphthol derivatives 25 via ortho-hydroxylation to obtain the highly-functionalized targets 26 [119]. Hereby oxaziridines 23 were found to be the best-suited hydroxylating agents. Unfortunately, the

• reaction has so far only been successful in a racemic fashion, whereas the use of chiral PTCs like A7 gave very little enantioselectivity only (er = 56:44, Scheme 12). Nevertheless, this inspiring report very nicely demonstrated the potential of phase-transfer catalysis for such dearomatization reactions

• dearomatization of phenols and naphthols. Ishihara’s ammonium salt-catalysed oxidative cycloetherification. Chiral phase-transfer-catalysed α-sulfanylation reactions. Chiral phase-transfer-catalysed α-trifluoromethylthiolation of β-ketoesters 1. Chiral phase-transfer-catalysed α-amination of β-ketoesters 1 using

Phosphazene-catalyzed desymmetrization of cyclohexadienones by dithiane addition

• Matthew A. Horwitz,
• Elisabetta Massolo and
• Jeffrey S. Johnson

Beilstein J. Org. Chem. 2017, 13, 762–767, doi:10.3762/bjoc.13.75

• nucleophile. Mild reaction conditions allow the formation of diversely functionalized fused bicyclic lactones. The products participate in facially selective additions from the convex surface, leading to allylic alcohol derivatives. Keywords: conjugate addition; cyclohexadienones; dearomatization

New approaches to organocatalysis based on C–H and C–X bonding for electrophilic substrate activation

• Pavel Nagorny and
• Zhankui Sun

Beilstein J. Org. Chem. 2016, 12, 2834–2848, doi:10.3762/bjoc.12.283

• with halides (Ka ≈ 103–104 M−1 in acetone-d6). Not surprisingly, a higher number of hydrogen bonds with an anion correlated with the higher stability of the receptor/anion complex. 1,2,3-Triazole-based catalysts for the dearomatization of N-heteroarenes The Mancheno group recently explored triazole

• the titration of L4 with TBAC [37]. Catalysts L3 and L4 were successfully applied to the asymmetric dearomatization of electron-deficient N-heteroarenes (Scheme 3). Various nitrogen-containing heterocycles such as pyridines [36], quinolines [38], isoquinolines [38], etc. were reacted with TrocCl to

• bond-donor catalysts by Bibal and co-workers [53][54]. Tetraalkylammonium catalyst (L6)-catalyzed dearomatization of isoquinolinium salts [50]. Tetraalkylammonium catalyst L6 complexation to halogen-containing substrates [51]. Tetraalkylammonium-catalyzed aza-Diels–Alder reaction by Maruoka and co

Catalytic asymmetric synthesis of biologically important 3-hydroxyoxindoles: an update

• Bin Yu,
• Hui Xing,
• De-Quan Yu and
• Hong-Min Liu

Beilstein J. Org. Chem. 2016, 12, 1000–1039, doi:10.3762/bjoc.12.98

• cyclization, giving the tricyclic N-heterocyclic core. Very recently, Shi and co-workers reported the chiral phosphoric acid (CPA, cat. 31)-catalyzed asymmetric dearomatization reactions of tryptamines with 3-indolyl-3-hydroxyoxindoles, affording the indole-containing tricyclic N-heterocycles in a highly